Centrifuge

ABSTRACT

Centrifuges are useful to, among other things, remove red blood cells from whole blood and retain platelets and other factors in a reduced volume of plasma. Platelet rich plasma (PRP) and or platelet poor plasma (PPP) can be obtained rapidly and is ready for immediate injection into the host. Embodiments may include valves, operated manually or automatically, to open ports that discharge the excess red blood cells and the excess plasma into separate receivers while retaining the platelets and other factors in the centrifuge chamber. High speeds used allow simple and small embodiments to be used at the patient&#39;s side during surgical procedures. The embodiments can also be used for the separation of liquids or slurries in other fields such as, for example, the separation of pigments or lubricants.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part Application of our earlier filed U.S. patent application Ser. No. 12/949,781 on Nov. 19, 2010, entitled Centrifuge, which is assigned to the same assignee as this invention and whose disclosures are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to centrifuges.

2. Discussion of Related Art

Fluids, such as whole blood or various other biological fluids are suspensions and can be separated into their constituent parts or fractions. For example, whole blood comprises four main fractions, red blood cells, white blood cells, platelets and plasma, that can be separated based on their different densities in a device such as a centrifuge. An anti-coagulated whole blood sample may be placed in a test tube, or other similar device, which is then spun in a centrifuge at a specified speed. The generated centrifugal force separates the blood into the different fractions based on their relative densities. The most dense red blood cells are on the bottom, the lightest, plasma, is on the top with the intermediate density white blood cells and platelets (together referred to as the buffy coat) intermediate to the other two fractions. Various other biological fluids may be separated as well. For example, nucleated cells may be separated and extracted from bone marrow or adipose tissue derived samples.

It is desirable to isolate the different fractions of whole blood for differing medicinal purposes. The platelets can be obtained in preparations of platelet rich plasma (PRP) or platelet concentrates (PC). Platelets contain growth factors (e.g. PDGF, TGF-β, and others), which may initiate, aid in or accelerate various bodily functions, including but not limited to angiogenesis, wound healing, and osteogenesis. Administering autologous platelets to an injury site may improve the healing response by using a patient's own platelets without the risk of infection by using blood products from another donor source. Alternatively, platelet poor plasma (PPP) may be desired for use in various procedures. PPP may be prepared by isolating the plasma fraction from platelet concentrates, and preserving the isolated plasma fraction.

Various systems exist for the production of PRP/PC. Some use specialized test tubes, U.S. Pat. Nos. 7,179,391 and 7,520,402, that can include floats, tubing and/or gel materials of specific densities. Other systems use specialized double syringes, for example those found in U.S. Pat. Nos. 6,716,187 and 7,195,606. These test tubes and syringes must be centrifuged in a specialized large centrifuge for a specified time, typically 10-30 minutes, and then by delicate handling and extraction or decanting procedures produce the desired PRP/PC. The consistency of these preparations can vary depending on the operator's skill level. Other systems, for example U.S. Pat. No. 6,982,038, contain specialized centrifuge chambers and complicated control systems to produce the PRP/PC in about 30 minutes. All of these systems provide PRP/PC of differing platelet concentrations depending on the method used. A major drawback to these methods is the need for an expensive piece of capital equipment which limits the utility to facilities that have the funds and space available. These methods also require considerable operator skills to complete the procedures necessary to obtain the PRP/PC.

The ability to produce PRP/PC from a patient's own blood at the point of care without the need for complex, expensive equipment and difficult procedures would facilitate the clinical utility of PRP/PC. Therefore the objects of this invention include among other things providing an apparatus and method for processing a patient's own blood at the point of care in a short period of time that is self contained, battery operated, small and or portable, inexpensive, easy to use, reproducible, able to separate many cellular populations, and disposable without the need for additional centrifugation equipment

SUMMARY OF THE INVENTION

In accordance with the invention, a single use, sterile, self-contained, compact, easy to use centrifugal separation unit provides for quick, reliable platelet concentration from whole blood. The resultant PRP/PC can be immediately used for application to the patient. The unit is suitable for office, operating room, emergency use, or military field hospital use.

The disposable self-contained PRP separator features a motor with a drive axis, the drive axis being coaxial with the central or longitudinal axis of the blood separation chamber (BSC) assembly. The motor can have the capacity to rotate the BSC at speeds in the range 10,000 to 25,000 RPM for several minutes. Power can be supplied to the motor through a battery or other power pack. The power can be connected through a switch and even small dry cell batteries will have sufficient capacity to complete the separation process. The BSC and motor/battery are fully enclosed in an outer container that includes an access port to the BSC to which a standard syringe can be attached. Alternatively the BSC can be rotated by non-electrical means such as an air driven turbine or spring drive. It could also include a magnetic or mechanical coupling to an external drive motor, or any source of energy that may be available at the surgical site for example in the surgical suite or on location during a trauma procedure, such as at a “MASH” compound.

In a first embodiment the BSC assembly features a barrel that may be cylindrical or tapered, an end cap incorporating ports and a tubular extension, and in some embodiments a piston or bladder, that between them define the BSC. A sleeve sliding over the outer diameter of the end cap acts as the moving part of two valve assemblies, each valve featuring a recess in the outer surface of the end cap and an O-ring in the recess. Passages within the end cap lead from the BSC to the recess centers, and two ports in the sleeve align with the recess centers in a 3 position sequence. The two ports in the sleeve are positioned so that they do not align with the two recess centers in the end cap at the same time. In sequence the sleeve selects a first port open, then both ports closed, and then a second port open. The ports are opened in a stepwise motion, but could be opened proportionally. The sleeve is operated by a knob connected to a slidable collar through a bearing assembly so that the knob does not rotate during operation of the motor.

Anti-coagulated blood is injected through the tubular extension in order to fill the BSC. The sleeve is in a first position where both ports on the sleeve do not align with either of the recesses in the end cap. The motor is actuated and the BSC rotates to create a centrifugal force on the blood thereby separating it into its components with the red blood cells closest to the inner wall of the BSC with the white blood cells lining the red blood cell layer toward the center, followed by the platelets and then plasma filling the center. In other words, the centrifugation yields stratified constituents of the mixture, with adjacent stratified constituents defining a mixture interface. After a centrifugation period of about 1 minute or less the sleeve is moved to a second position in which the first port in the sleeve aligns with the recess in the exterior wall of the chamber. This port communicates with the layer of red blood cells against the inner wall. The red blood cells will exit the chamber through this port due to pressure generated by the centrifugal force. As red blood cells exit the separator, the volume is replaced by air entering through the tubular extension in the end cap. The air forms a column in the center of the chamber that grows larger as more volume is replaced. It is also conceived that without an air inlet vent, that continued rotation and evacuation of the red blood cells will result in a vacuum core being formed, as the blood is degassed and possibly drawing vapor from the liquid due to the reduced pressure at the center of rotation. After a prescribed volume of red blood cells are discharged from the blood separator volume, the sleeve is moved to a third position to close the first port and open the second port. This is done before the layer of platelets in the volume can exit the first port. The passage to the second recess in the end cap of the device is precisely positioned away from the center axis to remove a prescribed volume of plasma from the BSC without disturbing the platelet layer. As plasma leaves the chamber, air replaces the volume through the tubular extension and the column of air in the center of the BSC continues to grow in diameter. When the diameter of the air column encompasses the second passage entrance, no more plasma can exit the chamber and the concentration process is thereby automatically ended. In the case where there is a vacuum core created, the concentration process would automatically end in a similar manner, as the vacuum core encounters the second passage entrance. The device is turned off and the platelet concentrate is ready for use.

Another embodiment uses a flexible bladder lining the interior of the BSC. The solid end of the BSC includes a hole for air to enter around the exterior of the flexible bladder. The end cap axis tubular extension includes an airtight valve. This embodiment operates in the same manner except that it does not deliberately introduce air into contact with the blood sample. During the centrifugation cycle while red blood cells and then plasma are exiting the chamber, air enters the opposite side of the chamber thus collapsing the flexible bladder. Due to the pressure generated in the liquid by centrifugal force, the sack collapses into a “W” shape with the open ends of the “W” facing toward the end of the chamber opposite the end with the air bleed hole. As more plasma exits the chamber the middle of the “W” reaches the second passage in the end cap and closes the passage off thus automatically ending the cycle.

Another embodiment replaces the flexible bladder with a piston and spring: as red blood cells (RBCs) exit the valve ports, the piston moves towards the end cap encouraged by the spring.

It is further disclosed that the system of the subject invention may incorporate an automatic shutoff mechanism to seal the port(s) based upon certain conditions. For example, one such mechanism can incorporate a flowable separation aid in the form of a gel of an intermediate density selected to be between an undesired element, e.g. red blood cells, and a desired therapeutic element, e.g. platelets. The separator gel viscosity is designed so that it will not pass through the small exit port at the centrifuge speed employed in the blood separation centrifuge. Upon activation of the centrifuge, the separator gel would create a distinct layer and barrier between the outer red blood cell layer, located near the periphery of the axis of rotation, and the platelet poor layer which would be located closer to the center axis of the centrifuge rotation. The separator gel automatically plugs the first port when all of the red blood cells have exited. As a further example, the automatic shut-off of the first port can be accomplished with a solid damper, or vent flap, also constructed of a material with a specifically targeted intermediate density. Upon initial operation, the damper would open and separate away from the vent hole based upon its density and attempt to position itself at a location between the red blood cells and the platelets. As in the previous example, once the red blood cells have fully exited the system, the damper would seal the vent hole and effectively prevent the platelet rich fluid from exited the system. As yet another example of a separation aid, plastic beads such as microspheres with the desired intermediate density could also be pre-located within the centrifuge chamber. The beads would be sized appropriately to plug the exit port after the undesirable element, e.g. red blood cells, exited the system.

In another embodiment, the BSC, or at least a portion thereof, can be made of a clear material so that the progress of the red blood cell removal can be observed through a clear window in the outer case. This can allow for precise timing for closing the first port to end the exiting of the red blood cells.

Another embodiment accomplishes the concentration through precise timing of the valve opening/closing sequence and the starting and stopping of the motor.

In another embodiment, the system may feature a reusable drive component with a motor that is arranged to be coupled to a disposable centrifuge component, wherein the blood products are centrifuged, separated, and contained entirely within the disposable unit, such that the drive component is not exposed to blood product and may be reused without fear of contamination.

In another embodiment, the disposable unit may include blood absorbent materials or fluid receiving chambers to capture the evacuated blood products.

In another embodiment, the rotation chamber is arranged to minimize the disruption to the interfaces between the separated blood products, while the red blood cells and plasma components are evacuated from the rotating chamber.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIGS. 1 a and 1 b: Principle of operation.

FIG. 2: Centrifuge with spring loaded piston in tapered chamber, charge position, RBC valve open, Plasma valve closed (Longitudinal part section).

FIGS. 3 a, 3 b, 3 c, and 3 d show transverse sections of the centrifuge with spring loaded piston in tapered chamber, (transverse sections of FIG. 2), and enlarged details of the RBC valve components used in all devices shown in FIGS. 2, 4, 5, 6, 7, 9,10,11, 12, 14, 15, 16, 17, and 18.

FIG. 4: Centrifuge with spring-loaded piston in tapered chamber, spin-down, RBCs separated from plasma, both valves closed (Longitudinal part section).

FIG. 5: Centrifuge with spring-loaded piston in tapered chamber, mid position, RBC valve open and RBCs being dumped, plasma valve closed (Longitudinal part section).

FIG. 6: Centrifuge with spring-loaded piston in tapered chamber, final position, RBC valve closed, plasma valve open and most of plasma dumped (Longitudinal part section).

FIG. 7: Centrifuge with bladder chamber, charge position, RBC valve open, plasma valve closed (Longitudinal part section).

FIG. 8: Centrifuge with bladder chamber, charge position, (transverse section of FIG. 7).

FIG. 9: Centrifuge with bladder chamber, spin-down, RBCs separated from plasma, both valves closed, (longitudinal part section).

FIG. 10: Centrifuge with bladder chamber, RBCs dumping position, RBC valve open, plasma valve closed (Longitudinal part section).

FIG. 11: Centrifuge with bladder chamber, Plasma valve open, RBC valve closed, plasma being dumped (Longitudinal part section).

FIG. 12: Centrifuge with air core, initial charge position, both valves closed. (Longitudinal part section).

FIG. 13: Centrifuge with air core, (transverse section of FIG. 12).

FIG. 14: Centrifuge with air core, spin and separate, RBCs being dumped, RBC valve open, plasma valve closed (Longitudinal part section).

FIG. 15: Centrifuge with air core, RBC valve closed, plasma valve open, residual RBCs and residual plasma remaining (Longitudinal part section).

FIG. 16: Centrifuge with air core, removal of PRP at finish, both valves closed (Longitudinal part section).

FIG. 17: Centrifuge with a typical enclosure (Longitudinal part section, showing RBC and plasma capture means and aerosol prevention means).

FIGS. 18 a and 18 b: Centrifuge with typical enclosure, (transverse section of FIG. 17).

FIG. 19. Simplified longitudinal cross section of centrifuge with disposable and reusable components shown separated. Shown with the red blood cell and plasma valves closed.

FIG. 20 a. Simplified schematic of centrifuge chamber having a plenum at the end of the red blood cell channel and separated fluids.

FIG. 20 b. Projection view of the plasma port of FIG. 20 a with plasma fluid flow pattern represented by arrows.

FIG. 21. Assembled centrifuge in running position, RBC valve open and RBC dump complete.

FIG. 22. Simplified transverse section of FIG. 21 at AA.

FIG. 23. Simplified transverse section of FIG. 21 through plasma valve at BB showing valve construction.

FIG. 24. Assembled centrifuge in running position, RBC valve shut, plasma valve open and plasma dump complete.

FIG. 25. Centrifuge with means for gathering Platelet Poor Plasma (PPP) in a separate receiver, shown in plasma collection phase of operation.

FIG. 26. Centrifuge with absorbent washers to capture blood products, shown at the end of the RBC dump phase.

FIG. 27 a. Simplified schematic of centrifuge chamber having plena at the end of the red blood cell channel and at the plasma outlet, and separated fluids.

FIG. 27 b. Projection view of the plasma port of FIG. 27A, with fluid flow pattern represented by arrows.

DETAILED DESCRIPTIONS OF THE EMBODIMENTS OF THE INVENTION

FIG. 1 a provides an illustration for description of the principle of operation of the devices covered in this invention. A chamber of essentially frusto-conical shape 1, contains a mixture of several liquids of differing densities, and rotates about the longitudinal axis XX. The liquids 2, 3, and 4 separate into radially distinct layers as shown in section AA. The taper is beneficial in several ways, first it allows a small volume of liquid to offer a large radial depth (as shown at 11) compared with the radial depth the same volume would have if distributed over the whole length of a right circular cylinder of similar dimensions, see FIG. 1 b at 14. Second, the taper provides a component of radial acceleration force that helps to scour the outer liquid constituent towards a port 9 placed at the larger cone diameter. Third, the taper also allows visualization of the constituent boundaries as axial locations such as 5 and 6 instead of radial locations such as 7 and 8 in some of the embodiments. In several embodiments the wall 12 of FIG. 1 moves toward the larger diameter and the frusto-conical volume reduces as one or more constituents are ported from the ports, for example at 9 and 10, leaving the center constituent 3 at it's original volume. In other embodiments wall 12 remains in place and air is introduced on the center line at 13 to permit the porting of constituents 2 and 4 at 9 and 10 as the air core expands to replace the discharged constituents.

FIG. 2 is a mainly longitudinal section of an essentially circular device, external housing not shown. In FIG. 2 a liquid tight variable volume, the BSC, is formed from a tapered barrel 206, piston 210, piston seal 211 and end cap 215. Piston 210 and seal 211 are biased toward the larger end of the BSC by spring 209. Larger end of barrel 206 is closed by end cap 215. In the case where this device is used to enrich plasma from whole blood, end cap 215 has passages 216 and 217 bored within to permit the passage of red blood cells from passage 217 and plasma from passage 216. Passage 217 is shown passing through the outside skirt of the end cap that is in line with the outside wall of tapered barrel 206. A passage bored 90° from that shown at 217; through the inside face of end cap 215 at the maximum ID position would be functionally equivalent to the one shown at 217 and would have a shape similar to passage 216. Passages 217 and 216 connect with valves formed by O-rings 218 compressed in recesses 226 operating in concert with ports 228 and 227 respectively in sleeve 213. These valve components are shown enlarged in FIGS. 3 b and 3 d. Sleeve 213 fits slidably on end cap 215 to permit the port holes 228 and 227 to connect with the passages 216 and 217 at appropriate points in the operation. Sleeve 213 is keyed to end cap 215 to permit the transmission of rotary motion between these constituents (key not shown). Insert 219 is fastened to end cap 215 to provide an axle for the ball bearing 220 supporting the left hand end of the rotating assembly. Since the sleeve 213 is rotating with the chamber, a ball bearing 221 is provide to connect the sleeve to a non-revolving knob 223 via collar 225 and rods 222. The knob and sleeve can be placed in 3 positions: first position, port 228 open and port 227 closed: second position, both ports 227 and 228 closed: third position, port 228 closed and port 227 open. Barrel 206 is fastened to the shaft 205 of electric motor 201 using screw 207. No additional bearings are provided at the motor end, the motor bearings sufficing to support the barrel. The complete assembly is supported by a frame 208, the insert bearing 220 and the motor 201 being located on this same frame. The rotating components all rotate about axis XX.

To use the device for preparing PRP, a syringe 233 with needle 234, filled with anti-coagulated whole blood is inserted into the device through elastomeric seal 214 to load the chamber with whole blood 229. Knob 223 is placed in the first position to allow air to discharge from port 228 as the chamber is filled with blood. Whole blood 229 fully charges the chamber pushing the piston 210 and seal 211 to the far right, compressing spring 209.

FIG. 3 a, a cross section at AA in FIG. 2, clarifies the construction of the knob 223 and rod components 222. FIG. 3 b is a cross section at BB in FIG. 2 showing details for the valve components, those being the recess 226 in end cap 215, O-ring 218 and port 228 in sleeve 213 (the construction of the valve for port 227 is the same). FIG. 3 c shows the section at CC of FIG. 2.

Once the chamber has been charged with whole blood, the knob and sleeve are placed in the second position with both valves closed, the syringe 223 is removed and the motor started. The motor is then run for times between 15 and 90 seconds depending on the speed used. Speeds of 10,000 rpm to 25,000 rpm have been used, developing centrifugal accelerations at the outside of the spinning chamber from 1000 g to 6000 g.

FIG. 4 shows the device of FIG. 2 in operation rotating at speed. The RBC port 228 and the plasma port 227 are both closed. The boundary between RBCs and plasma is shown at 237. The piston 210 is still at the as-charged position and the spring 209 is fully compressed. The spring has two functions, it moves the piston to the left as red blood cells are discharged from the chamber through port 228, and the spring creates a significant minimum pressure in the revolving liquid: this prevents the core of the spinning liquid from reaching the vapor pressure of the liquids and may suppress cell damage in some circumstances.

Once the red blood cells and the plasma have separated, with the device still rotating, the knob and sleeve are placed in the first position and red blood cells are discharged from port 228 into the casing (casing not shown, but see FIGS. 17 and 18) surrounding the device. FIG. 5 shows the situation at the mid-point of the RBC 231 discharge when the piston 210 is in mid position. Once the majority of red blood cells have been discharged the valve is placed in the third position and plasma 230 is eliminated from port 227. FIG. 6 shows the situation at the end of the enrichment process: the plasma port 227 is still open and the piston is close to the far left position: platelets that have a density between that of plasma and RBCs are trapped at the RBC-plasma boundary 237; the plasma port is about to be closed and the motor stopped.

Typical volumes for the chamber are 20-100 mL, and the amount of enriched plasma removed at the termination of the procedure is approximately a quarter to an eighth of the original volume depending on the degree of enrichment desired.

In order to retain all the platelets and other factors gathering at the RBC-plasma boundary, it is essential to close port 228 before all the RBCs have been removed, otherwise there is the danger of these constituents flowing out with the last RBCs. To ensure that this does not occur, the blood sample hematocrit value is used to judge the residual volume of the chamber when the RBC port must be closed. This volume is observable as a piston axial position, and the valve is moved from position one to position three as the piston reaches this predetermined position.

The device described in FIGS. 2 through 6 uses a piston and seal traveling in a tapered tube, but a right circular cylinder may well function adequately for mixtures of liquids other than blood and where the residual volume of the first liquid discharged is not too critical. The tapered tube has the advantages mentioned in the discussion of FIG. 1. The position of the piston can be judged visually by the operator relative to graduations on the barrel (not shown), or an optical detector and automatic valve operation system can be used (not shown).

Since the residual enriched plasma is injected back into the patient the materials used for this device have to be medical grade materials, at least for those constituents contacting the blood. Polycarbonate or PTE are suitable for the barrel 206, end cap 215, sleeve 213, frame 208, knob 223 and collar 225. Insert 219 is of a suitable grade of passivated stainless steel such as 416 or 420. The ball bearings have to do duty at high speed but operate for very short times so stainless steel bearings of grade ABMA 1-3 are adequate. O-rings 218 and seal 211 are of silicone rubber. Since the motor does not contact blood, industrial motors (for example those made by Mabucci) are adequate.

FIG. 7 shows an embodiment with a flexible bladder 312 that initially conforms to the bore of the barrel 306, the bladder providing a variable volume chamber through its ability to invert as shown in FIGS. 10 and 11. This embodiment may serve to reduce the effect of entrapped air bubbles.

In FIG. 7 a liquid tight variable volume centrifuge chamber (the BSC) is formed from a tapered barrel 306 containing a molded bladder 312, and end cap 315. The bladder is captured in a return fold 339 between a barrel projection 338 and the end cap 315. Larger end of barrel 306 is closed by end cap 315. In the case where this device is used to enrich plasma from whole blood, end cap 315 has passages 316 and 317 bored within to permit the passage of red blood cells from passage 317 and plasma from passage 316. Passages 317 and 316 connect with valves formed by O-rings 318 compressed in recesses 326 operating in concert with ports 328 and 327 respectively in sleeve 313. Sleeve 313 fits slidably on end cap 315 to permit the ports 328 and 327 to connect with the passages 316 and 317 at appropriate points in the operation. The knob 323 and sleeve 313 can be placed in 3 positions: first position, port 328 open and port 327 closed: second position, both ports 327 and 328 closed: third position, port 328 closed and port 327 open. Sleeve 313 is keyed to end cap 315 to permit the transmission of rotary motion between these constituents (key not shown). Insert 319 is fastened to end cap 315 to provide an axle for the ball bearing 320 supporting the left hand end of the rotating assembly. Since the sleeve 313 is rotating with the chamber a ball bearing 321 is provide to connect the sleeve to a non-revolving knob 323 via collar 325 and rods 322. Barrel 306 is fastened to the shaft 305 of electric motor 301 using screw 307. No additional bearings are provided at the motor end, the motor bearings sufficing to support the barrel. The complete assembly is supported by a frame 308, the insert bearing 320 and the motor 301 being located on this frame. The revolving components all rotate about axis XX. In this illustration the sleeve is in the first position to keep the port 328 open for porting of air as the chamber is charged with blood, and the plasma port 327 is closed. Whole blood 329 fully charges the chamber. An elastomeric seal 314 permits the introduction of a needle 334 for the passage of whole blood into the chamber before the start of rotation, and removal of enriched plasma at the cessation of action.

FIG. 8 is a transverse cross section of the device shown in FIG. 7 at section AA. Whole blood 329 fills the BSC and bladder 312 which is fully in contact with barrel 306. Frame 308 runs under the rotating assembly.

FIG. 9 shows the device of FIG. 7 in operation rotating at speed. The sleeve 313 is in position two with both ports 327 and 328 closed. The boundary between RBCs 331 and plasma 330 is shown at 337. The bladder is still against the barrel now under the influence of the pressure developed by the spinning liquid mixture.

FIG. 10 depicts the situation after spinning for 60 seconds or so. The sleeve 313 is placed in position one, port 328 is open and RBCs 331 are being discharged through port 328. Plasma port 327 is closed. The bladder has moved to the left to compensate for the volume of RBCs that have been discharged. The shape adopted by the bladder is a balance between the forces developed by liquid pressure pushing the bladder to the right and atmospheric pressure (via vent 332) pushing the bladder to the left. Since the pressure at the center of the spinning liquid is near absolute zero the atmospheric pressure exceeds the left hand pressure that has been developed up to a certain radius, hence the re-entrant shape of the bladder. The volume of plasma 330 has remained the same as when introduced. The boundary between RBCs and plasma is shown at 337. In this view the RBC discharge is about to be stopped since the residual RBC volume 331 is low enough.

FIG. 11 illustrates the final position for the bladder 312 while the rotation continues but just prior to stopping. Sleeve 313 is in position three, RBC port 328 is closed and plasma port 327 is still open. Plasma has been discharged through port 327 and is about to be cut off by the bladder rolling onto end cap 315 and cutting off the passage 316. This illustrates the minimum volume of enriched plasma 330. At this point the sleeve 313 is moved to position two with both ports closed and the rotation is then stopped; the residual liquid is removed using a syringe in a similar manner to the charging described in FIG. 7.

Materials for the device of FIGS. 7 through 11 are similar to those for the device of FIGS. 2 through 6: the bladder by example can be made of silicone rubber, polyurethane or polyvinylchloride.

For the previous device 200 the piston position provided the signal for closure of the RBC port 328. In the case of the bladder the inverted bladder rolls along the tapered barrel bore, the axial position of the reverse edge providing (labeled 312 in FIG. 11) the volume and the signal for port closure. The cut-off of the plasma discharge is automatic as the bladder rolls over the port passage 316.

The device described in FIGS. 12 through 16 utilizes an air core and uses no bladder or piston.

The device of FIG. 12 is very similar in construction to the two previous embodiments, with a BSC formed from a barrel 406 and end cap 415. In this illustration whole blood 429 from syringe 433 fills the centrifuge chamber through needle 434 with both ports 428 and 427 closed. Air displaced by the blood leaks out through the clearance between the needle 434 and insert 419 bore as the blood is injected. FIG. 13 shows the circular section nature of FIG. 12. Once the charging syringe is removed, the motor is started and the chamber is rotated at 10,000 to 20,000 rpm for approximately one minute. At this point the sleeve 413 is moved to the second position, and RBCs are discharged through port 428 until the point shown in FIG. 14 where the minimum RBCs 431 remain. Meanwhile, the plasma adopts the region 430, and a boundary 440 forms at the plasma-air radial interface, the air core 438 having entered through the bore of insert 419 (via a filter in the housing not shown, but see FIGS. 17 and 18). At this juncture the sleeve is moved to the third position, port 428 closed and port 427 opened. With this preferred device there is no bladder or piston to observe, so the operator observes the axial interface 436 between the RBCs 431 and the plasma 430 of the mixture to determine when to manually close the RBC port 428 and open the plasma port 427. With blood, this mixture interface is easy to see and can be automated with an optical detector. The difference in electrical resistivity between red blood cells and plasma can also be used to trigger an indicator or automated valve. An alternative way of determining the point at which to shut the RBC port is to use time. After one minute of running to separate the constituents of the blood, the RBC port is opened and a timer started. Since the pressure generated in the centrifuge is a predictable function of liquid density and running speed, and since the RBC port is a precisely calibrated orifice, the flow rate being discharged, and hence time can be computed for a given hematocrit value.

With the motor still running, the plasma discharges through port 427 until it reaches the situation in FIG. 15 where the residual RBCs are at 431 and the residual plasma at 430. The sleeve is then moved to the second position to close both ports. In the case of plasma the passage 416 is placed at a precise radial location to give an accurate final volume since no further flow of plasma will occur once the air core 438 has grown to that passage radial location. The motor is then stopped and the device placed on end, with the motor downward, so that the rotation axis is vertical as shown in FIG. 16. The remaining enriched plasma with some RBCs is removed by syringe and needle as illustrated.

An enclosure suitable for various embodiments discussed in this application is described in FIGS. 17 and 18; however these two figures show the enclosure applied specifically to the air core embodiment of FIGS. 12 through 16. The frame 508 is mounted to a battery power pack 503 that acts as the base for the enclosure. An outer casing 500 surrounds the centrifuge and is fastened to the battery pack 503, the joint being liquid and air-tight. A valve selector knob 545, integral with eccentric 546 and pin 547, is mounted in the casing such that the selector knob 545 can be turned by the operator to actuate the internal knob 523 via the pin 547 in groove 548 and hence the collar 525 and valve sleeve 513. In FIG. 17 the motor 501 driving the chamber BSC is controlled manually by switch 504 connected to battery pack 503 by wires 550. A bush 543 mounted at the left hand end of the enclosure 500 provides alignment for the entry of the syringe (433 of FIG. 12) needle when charging the chamber with whole blood or when extracting the enriched plasma. Immediately adjacent to bush 543 is a porous flexible pierceable filter 544. This filter has two functions: It filters the air entering the core of the centrifuge when it is running, and it prevents the egress of any aerosols into the atmosphere of blood fragments generated as the centrifuge discharges RBCs or plasma into the casing. A small slit in the filter allows the charging syringe needle to enter without damaging the effectiveness of the filter. Covering most of the interior walls of the casing 500 is a highly absorbent lining 542 to absorb the RBCS and plasma discharged into the casing as the air core 538 enlarges and the enrichment process proceeds. A lens and mask 549 placed in the wall of the casing 500 permits the operator to view the axial interface 536 of the RBCs and plasma as the process of enrichment proceeds. The mask and lens are chosen to enhance the contrast of the image seen of the liquid separation interface 536.

A photo detector (not shown) can be placed in the location of the lens to provide an electrical signal of the progress of the liquid separation interfaces, and an electromagnet actuator can drive the valve selector knob 545. These electrical elements in conjunction with a manual switch can be used to control the entire process once the motor has started.

From tests to date it would seem feasible in some applications to use a simple timer program to schedule the sleeve motions. For example, the following sequence can operate off a timer once the chamber is charged with blood, a) start motor, run for 60 seconds b) open RBC port and discharge RBCs for 30 seconds, c) close RBC port and open plasma port and run for 30 seconds, d) close both ports, and stop motor. Such a device might require the addition of a means of manually inserting the patient's hematocrit number to allow for varying proportions of RBCs to plasma.

Table 1 gives typical data obtained for the air core device of FIGS. 12 through 16 using porcine blood. The data was obtained with runs of one minute for the initial separation and approximately one more minute to discharge the RBCs and plasma.

TABLE 1 Platelet Count Platelet % Red (×10³/ Concentration % Platelet Blood Cells Sample microliter) Factor Recovery Removed Baseline 229 NA NA NA Run 1 1656 7.2 100 93 Run 2 1457 6.4 88 92 Run 3 1446 6.3 87 93 Run 4 1685 7.3 100 94

For all three embodiments discussed, piston, bladder and air core, the size and position of the ports and passages are very important. As the centrifuge rotates, the pressure developed within the chamber varies as the square of the speed and the square of the radius of rotation. To gain manual control over the discharge of constituents the discharge needs to take place over a manageable time. The RBC port for example needs to be sized to allow passage of the RBCs over a period of about 30 seconds. Conditions must be selected to allow the RBC port to function without blockage as the RBCs try to clump, and flow has to be kept low enough to stop the platelets from being swirled into the exit vortex. For centrifuges using whole blood samples of approximately 30 mL, it has been found that RBC ports of the order 0.008 inch diameter work well if speeds are in the region 15,000 to 20,000 rpm and chamber barrels are about 1.0 to 1.25 inch in diameter at the largest point. Plasma ports can be larger since the risk of losing the platelets is less: values of about 0.010 inch diameter are adequate. Placement of the plasma ports relative to the center axis of rotation has a direct effect on the attainable concentration factor. The closer to the center, the less plasma is removed and less concentration is achievable. Additionally, in various embodiments of the invention discussed it will be noticed that a small annulus 241, 341, 441, 541 is created at the large diameter end of the chamber. This annulus creates a localized area of increased radial depth, but of small volume, for the RBCs prior to their entry into the RBC passages 217, 317, 417. This increase in depth reduces the tendency for the platelets and other desired factors from exiting with the RBCs being discharged through the RBC port 228, 328, 428 under influence of the exit vortex created locally close to the same ports (not shown).

In all the embodiments discussed the accuracy of the RBC port closure point can be improved by employing a separation aid, such as a flowable separator gel of an intermediate density between the red blood cells and the platelets. The separator gel spreads over the red blood cell layer moving the other layers further towards the center axis. The separator gel automatically caps the first port when all of the red blood cells have exited. The separator gel viscosity is designed so that it will not pass through the small exit port at the centrifuge speed employed in the BSC. The automatic shut off of the first port can also be accomplished with a separation aid in the form of a solid material of intermediate density that is designed to enter and close off the port when the red blood cells have fully exited. An example would be plastic beads such as microspheres with the desired intermediate density that are large enough to cap the port when agglomerated as they flow toward the port.

For the bladder and air core embodiments the visualization of the RBC plasma axial boundaries can be improved by incorporating back lighting, such as in the form of an LED mounted inside the BSV adjacent to the motor centerline. Additional windings in the motor could provide the low power needed to power the lamp.

With adjustments to size and locations of the port and passage dimensions, the subject invention also has the capability for separating and concentrating a wide variety of therapeutically beneficial cells and other biological constituents. Many of these biological constituents have the potential for regenerative therapy and can be characterized as regenerative agents. These regenerative agents can assist with the regeneration, restoration, or repair of a structure or assist with the function of an organ, tissue or physiologic unit or system to provide a therapeutic benefit to a living being. Examples of regenerative agents include for example: stem cells, fat cells, progenitor cells, bone marrow, synovial fluid, blood, endothelial cells, macrophages, fibroblasts, pericytes, smooth muscle cells, uni-potent and multi-potent progenitor and precursor cells, lymphocytes, etc. The invention also has the potential to process soft or liquid tissues or tissue components or tissue mixtures including but not limited to adipose tissue, skin, muscle, etc. to provide a therapeutic regenerative agent. The resulting separated or concentrated products from the various embodiments described herein may be used as is known in the art. Medical treatment procedures may call for the concentrated product to be applied directly to a treatment site, or incorporated into a treatment device (e.g., administered to an absorbent implant material prior to, concurrent with, or post-implantation), or even combined with another material as a method of treatment, for example, by combining with a particulate material to form a paste (e.g., combined with a extracellular matrix that has been formulated as a powder).

The blood centrifuge container may also incorporate an adjustable port, e.g. a tube with an open end extending radially into the BSC and hinged at the outer periphery in such a manner that the tube can be swung in an arc for the open end to scan a range of radii (not shown). The location of the open end of the tube can be adjusted before or during operation such that it is located at a desired position with respect to the axis of rotation. For example, the entrance port could be located towards the periphery of the centrifuge container to initially vent undesired cells, and later adjusted towards the center of the container to vent platelet poor plasma. Alternatively, if the plasma fraction is what is desired to be removed, the port can be positioned so that essentially only plasma is tapped from the stratified mixture.

The apparatus may also be configured to shut off, or at least to cease rotating, once a predetermined quantity of one or more constituents such as plasma has been tapped. Specifically, a port may be positioned such that, upon stratification, the plasma constituent is adjacent the port. When the valve for that port is opened, plasma is dispatched out through the port. The port may also be configured with a sensor that senses the presence or absence of plasma. As such, the apparatus can be configured such that the barrel continues to rotate as long as plasma is sensed at or in the port, but when plasma is no longer sensed, the sensor provides a signal to the motor to stop (thereby stopping the rotation of the barrel) or signaling the opening of a tap. As plasma continues to be removed from the barrel through the port, eventually the supply of plasma at the radius of the port is exhausted, thereby causing a signal to be sent from said sensor, and the barrel stops rotating. Of course, each of these signals may arise from the sensing of any stratified layer, not just plasma.

It may be desirable to collect one or more of the discarded fractions of the liquid specimen in addition to the concentrated fraction. This can be accomplished by one of several methods. A collection bag or chamber can be connected to an exit port on the sleeve. This bag or chamber will rotate with the barrel so provisions must be taken to balance it around the axis of rotation. Another method would be to have a circumferential funnel opposite the desired exit port that would collect the fraction being discharged and guide the fluid to a collection point by gravity flow. This is further illustrated later in reference to FIG. 25.

Further embodiments are shown in FIGS. 19 through 26. These figures describe a device using the air core principle covered in FIGS. 12 through 17 but incorporating improvements designed to maximize the enrichment obtainable when preparing PRP. FIG. 19 shows the two major components of a centrifuge designed to be used in two components, a reusable drive unit 601 and a disposable portion 600. The separation of the centrifuge into two components allows the disposable component to be more cost effective.

FIG. 20 a is a schematic representing a half mirror section of a revolving chamber defined by the boundary letters ‘defg’. Significant dimensions are noted by length references L1 through L8, and the radii identified as D1 through D8. As can be seen in FIG. 20 a, D1 corresponds to the length of the radius measured from the rotational axis XX to the outer end of the channel 640, as shown in this embodiment having an optional plenum at the end of the channel, where exiting RBCs 641 enter into the RBC passage 639. Similarly, D2 and D3 identify the inner diameters for the right and left sides, respectively, of the plenum at the end of the channel 640 farthest from axis XX. D4 and D7 mark the outer and inner diameters, respectively, of the flat located on the right hand end of wedge 609. D5 identifies the diameter at the interface between the red blood cells 641 and the buffy coat 642. D6 identifies the diameter at the interface between the buffy coat 642 and the plasma 643. D8 identifies the inner diameter of plasma passage 610, and corresponds to the interface of the plasma 643 interface with the air core 646. The length measurements L1 through L8 are based upon a distance measured from the reference line corresponding to the right side of the plasma passage 610. L1 and L2 are measured to the left and right hand sides, respectively, of the plenum at the end of the channel 640. L3 identifies the length to the flat on the right hand side of wedge 609, measured from the reference line. L4 and L5 identify the location of left and right markers 644. L6 corresponds to the length to the edge of the rotation chamber measured at the diameter corresponding to the buffy coat/plasma interface D6. L7 corresponds to the length to the edge of the rotation chamber measured at the diameter corresponding to the inner diameter of the flat located on the right hand edge of wedge 609. L8 corresponds to the length to the edge of the rotation chamber measured at the diameter corresponding to the inner diameter of the entry into the plasma passage 610.

The rotational axis XX passes through boundary ‘dg’. The major cross hatched area represents the tapered chamber with the outer wall having a half angle ‘a’. Inserted into the conical recess of the chamber is a wedge ‘609’ having an external frusto-conical portion of half angle ‘b’ that defines RBC channel 640 and an internal reverse frusto-conical recess defining half angle ‘c’ that defines the boundary of the plasma 643. It should be noted that half angle ‘b’ need not necessarily be the same as half angle ‘a’, in other words the channel 640 may be tapered, not parallel.

As fluid exits the RBC outlet port, the fluid exiting through the RBC passage 639 experiences high shear forces, and the RBC channel 640 serves to ensure that the RBC passage 639 entry port is at the end of the channel 640 and at a distance removed from the RBC-BC interface, with the channel dimensioned to allow for significantly slower local flow speeds at the RBC's entrance into the channel 640, relative to the high exit speed the RBC experiences as it exits through the RBC passage 639.

For example, in one embodiment, RBCs collect at the outer edge of the spinning chamber and discharge through one or more RBC passages 639 fed from a circumferential groove or plenum, which, in turn, is fed from a thin circumferential channel 640, or alternatively, circumferential sections forming multiple channels 640, starting adjacent to the buffy-coat collection areas. The circumferential channel 640 has a circumference many times larger than the radial depth of the channel. For a device providing a 60M1 centrifuge, and having a channel with a 4.5 inch circumference by 0.020 radial depth the orifice diameter for RBC passage 639 would be of the order 0.010 inch. This combination spinning at approximately 17000 RPM would result in velocities of 2000-3000 cm/sec from the orifice at RBC passage 639, and only 1.5 cm/sec along the channel 640. Thus the channel 640 slows the flow adjacent the separation layer by a factor of over 1000 to 1. In another embodiment (not shown) not having a plenum, the RBC passages may be fed directly from the thin circumferential channel, starting adjacent to the buffy-coat collection area. Similar performance, in achieving a reduction of flow rate at the separation layer, when compared to the orifice exit, would be expected as that described with reference to the embodiment having a plenum.

Modifications to the dimensions, or rotational speeds may be employed to ensure that a reduction in localized flow rates, when measured at the RBC passage 639 and compared to the RBC entry into the channel 640, may be made to achieve different reduction rates, such as reduced beyond approximately 500:1, or 100:1, instead of the 1000:1 described above. As can be seen in the embodiment of FIG. 20 a, the channel 640 is arranged on a radially shallow angle a, and is shown having a plenum at the terminus of the channel, from which the RBC passage 639 provides for the discharge of the RBC. In another embodiment (not shown), the device may not provide a plenum at the terminus of the channel, but rather the channel terminus may include the outlet for the RBC passage, or the channel may reduce in dimension (taper) and funnel directly into the outlet for the RBC passage. As described above, the devices of this invention aim to reduce the effect of the exiting RBCs upon the buffy coat components, as may be accomplished by providing for spatial separation between the RBC outlet and the RBC/buffy coat interface. It is this spatial separation, with or without a plenum in the channel, that reduces the tendency for the platelets and other desired factors from exiting with the RBCs being discharged through the RBC passage 639 under influence of the exit vortex created locally close to the port. By operating the device in a manner that prevents plasma or buffy coat components from entering the channel 640, the high shear forces will be limited in effect only to the RBC component, and will be unable to disrupt the interface between the RBC and the BC.

Similarly, by placing the plasma passage 610 at a location removed from the buffy coat component (and optionally located within a plenum as depicted in FIG. 27 a), and with the buffy coat-plasma interface not extending inward beyond D7, the buffy coat can be contained within the chamber, as with the shallow angle c, the high shear forces at the plasma passage 610 will not cause the disruption of the BC-plasma interface. Thus there is a reduction in the tendency for the platelets and other desired factors from exiting with the plasma discharged through the plasma passage 610 under influence of the exit vortex created locally close to the port. Though depicted in FIG. 20 a as located at the base of the wedge 609, the plasma passage may be located elsewhere, so long as the opening is at a suitable radius that is smaller than the radius of the buffy coat-plasma interface, such as at a location corresponding to L8 in FIG. 20 a. Through these features, the embodiments described aid in preserving substantially all of the buffy coat component within the chamber and enhancing concentration or enrichment efficiency of the finished product.

Furthermore, with reference to FIG. 27 a, there is depicted an embodiment identical to that shown in FIG. 20 a, except that there is included a plasma plenum 655 in the form of circumferential groove (or portions of a circumferential groove) housing the orifice(s) that lead into the plasma passage 610. In this embodiment, the exiting plasma will flow along the tapered channel defined by the boundaries of the wedge 609, and the air core interface with the plasma. While the chamber is being rotated, and the plasma valve open, the plasma will flow towards the plasma passages (depicted here located at the base of the wedge 609), and spill over the wedge base and into a plasma plenum 655. Once within the plasma plenum, the plasma will flow along the length of the plenum (i.e. circumferentially) until it encounters and exits through the orifice(s) leading to the plasma passage 610. While the plasma is traveling within the plenum 655, it will not exert shear forces upon the plasma/buffy coat interface, which is at a distance removed, and physically shielded by the presence of the wedge 609.

Comparing the FIGS. 20 b and 27 b will allow visualization of the direction of fluid flow as the plasma approaches the plasma outlet, whether as a continuous slope (the geometry shown in FIG. 20 b), or with a plenum 655 (the geometry shown in FIG. 27 b). These figures represent a projection view, looking down towards the opening to the plasma passage 610, as if one is looking from the axis of rotation towards the outside diameter of the chamber.

With reference to FIG. 20 b, the plasma is depicted as traveling from right to left, and as the fluid approaches the left edge of the chamber, the fluid will be drawn towards the outlets for plasma passage 610. In this embodiment not having a plasma plenum, the shear forces will be proportionally reduced with increasing distance from the opening, thus as the plasma travels along the inside face of the wedge (along angle c), the shear forces will not necessarily be uniform throughout the entire diameter of the region, but will be higher when alongside the locations of the openings to the plasma passage 610. While the geometry of FIG. 20 a has been empirically determined to be effective in minimizing shear forces affecting the buffy coat/plasma interface, it may be possible to even further reduce the shear forces experienced at the flat of the wedge during the operation of the device.

With reference to FIG. 27 b, the plasma is depicted as traveling from right to left, and enters into the plasma plenum 655, prior to flowing along the plenum towards the openings 610. As can be seen by the uniform arrows (right side) depicting fluid flow towards the plenum 655, the presence of the plenum is expected to reduce variations in shear force, when measured circumferentially within the plasma channel (the plasma flowing between the wedge face at angle c and the air core), as the plasma will approach the base of the wedge 609, and flow into the plasma plenum 655, and thus create an effect similar to water flowing over the breast of a dam. That is, prior to cresting the obstruction, whether upstream of the dam, or prior to entering the plenum, the fluids flow slowly and smoothly, then once past the obstruction, whether downstream of the dam or within the plenum, the fluid flow rates will be relatively much higher and less uniform. As can be seen by the arrows depicting the fluid flow pattern, the flow of plasma towards the plasma plenum is expected to be uniformly distributed over the entire diameter, then once the plasma has crested the wedge, and is within the plenum 655, then there will be large variations in fluid movement as the plasma flows out the one or more openings to the plasma passage 610. Since the variable direction shear forces are largely contained within the plenum, and not affecting plasma flowing along the wedge face, this embodiment would be expected to allow for enhanced enrichment factors of the buffy coat components. The geometry of this embodiment allows for retained plasma, measured as the depth between D8 and D6, to be minimized, due to the reduced variability of plasma flow rates, when measured circumferentially along the plasma channel, that would otherwise tend to disrupt the buffy coat/plasma interface.

Furthermore, with reference to FIG. 20 a, it should be pointed out that the volume of plasma remaining after all the discharged plasma has left the chamber is defined by the boundary diameters D8 and D6. This volume can be tuned to get the value of enrichment desired by adjusting these same mentioned dimensions.

It should also be made clear that to obtain high degrees of enrichment, the depth of plasma beneath the buffy-coat (as seen in FIG. 20 a) must decrease (diameter dimension (D6-D8)/2 decreases) so the risk of platelet loss increases because the out-flowing plasma shears the buffy/plasma interface more closely. However, the pressure driving the plasma outflow gradually drops to zero as the plasma diameter approaches D8 since pressure driving the plasma flow is proportional to the square of the speed of rotation, multiplied by the difference of the squares of the radius of the opening of the plasma passage located at D8 and the radius of the plasma/air interface within the chamber.

By taking advantage of this steadily reducing flow effect as the plasma approaches D8, the plasma depth (D8-D6) can be minimized, with little loss of buffy coat due to shear, and the residual plasma volume minimized and the enrichment maximized.

To summarize, RBC/buffy-coat shear is minimized using the outer diameter channel to control RBC/buffy-coat shear, and plasma/buffy coat shear is controlled by geometry and the reducing plasma to air core driving pressure.

Thus, while the chamber is rotating, and prior to the discharge of any of the plasma, there is a larger pressure head driving the plasma out through the plasma outlet and into plasma passage 610, subsequently, as the volume of plasma in the chamber decreases, the pressure head above the plasma outlet is reduced in a proportionate amount, until the plasma level reaches the level of the plasma outlet at D8, and all plasma flow out through the plasma passage 610 terminates. As the flow rate through the plasma passage 610 is reduced as the plasma volume is reduced, this provides the added benefit that the tendency for shear forces to affect the buffy coat is minimized, as at the point the plasma flowing out and the buffy coat are at nearest proximity to each other (i.e., the distance between D6 and D8 is at its minimum), the plasma evacuation flow rate will be at its lowest rate.

In operation blood fills the chamber and after a period of time at speed separates in to red blood cells (RBC), buffy coat and plasma. After separation, RBC passage 639 is opened and RBCs discharge from RBC passage 639, the interface of the RBC's being evident at L5 at the transparent conical surface. Visible markers are placed on the chamber at L5 and L4 to guide an operator in the closing of RBC passage 639: when the RBC interface reaches somewhere between L5 and L4 the discharge of RBC's out of RBC passage 639 is stopped by manipulation of valves to be described later. At this point, residual RBCs occupy a predefined volume defined by the conical channel 640 and the circumferential recess at the left hand end of the RBC channel 639. When collecting buffy coat (BC) 642, defined on the illustration by the honeycomb hatch, it is important to prevent the BC from migrating into the RBC channel 640, since the BC cannot be recovered at the end of the procedure if they migrate there. To ensure that this does not happen, the rate at which the RBC interface appears to move along the conical surface of the chamber is controlled to a velocity that is sufficiently low for an operator to stop the process (by closing RBC passage 639) as the interface travels between makers placed at L5 and L4. This velocity is a function of speed of rotation, diameter of the chamber, size of the RBC discharge port connected to passage 639, and the half angle ‘a’ of the chamber. These variables are adjusted to give an interface velocity at L5 or L4 that is manageable by a human operator but that does not impede the rapid separation required (whole process of separation, discharge of unwanted RBCs and plasma in less than 2 minutes). In testing various parameters, it has been experimentally determined that an interface velocity of approximately 4 mm/sec allows accurate intervention by the operator, though it is recognized that higher and lower velocities may be desirable, on the range of less than 10 mm/sec. (In the case where the RBC to Buffy coat interface is detected by optical sensors or the like the approach velocity of the interface can exceed the 10 mm/sec. rate). When the RBC discharge is stopped, the BC is captured at the end of the flat on the right hand end of the wedge 609, defined by diameters D4 and D7. Though the flat is depicted in FIG. 20 a as being at 90 degrees to the axis of rotation, it is envisioned that the flat may be at another angle relative to the axis of rotation. If the RBCs are stopped at L5, the BC outer diameter is D5, if the RBCs are stopped at L4 the BC outer diameter is at D4. The buffy coat (BC) volume is around 0.5% of the blood volume initially introduced, so the flat on the end of the wedge (D4, D7) can be defined to ensure that in the worst case (RBC stopped at L5) the BC stays on the flat and does not extend into the inner half angle cone ‘c’. Once the RBC passage 639 is closed, the plasma passage 610 is opened and plasma flows to discharge. The illustration shows the situation when all the plasma has flowed out of plasma passage 610 and flow has stopped because the air core 646 has expanded to the diameter of the passage inlet at D8. Prevention of BC getting into the inner cone is important since the axial velocity of the plasma surface accelerates as it approaches the exit passage 610 and fast shear velocity at the BC/Plasma interface results in loss of platelets into the plasma. With radial separation of BC to air core (D6-D8)/2 of the order 1 mm-2 mm, the loss of platelets into plasma is acceptable and enrichment factors (EF) of 8:1 or more can be consistently obtained. Enrichment factors are defined by the following equation: (EF=(# of platelets captured in the BC sample per unit volume)/(# of platelets in the original whole blood sample per unit volume)). Fundamentally, this design has been conceived to minimize the shear at the RBC/BC and BC/Plasma interfaces and hence reduce loss of BC to the RBC discharge or the plasma discharge.

In one embodiment, the orientation of the device in use is with the axis of rotation XX being vertical, with the port valve 602 at the top of the device. As a consequence of the geometry of the rotating chamber, when the rotation is halted, any fluid (e.g., RBC) that is within the channel 640, will tend to remain contained in that channel, and substantially all other fluid above the line corresponding to the flat 608 of the wedge 609 while in operation (i.e., to the right of L3 in FIG. 20 a), will flow by gravity, upon cessation of rotation, and pool directly underneath the port valve 602, and is available to be harvested, such as by being drawn into a needle directed through the port valve and into the pool of concentrated materials. It is recognized that the various embodiments described herein may be operated at another angle (e.g., horizontal), and then optionally rotated to vertical for harvesting, after cessation of rotation. By maintaining the RBCs sequestered within the channel 640 upon cessation of rotation of the chamber, the concentration of the buffy coat components can be maximized, as those materials within the channel (e.g., RBCs) are not available to further dilute the concentrated buffy coat or other blood components. In some embodiments, it may be advantageous to add a surface tension modifying coating (e.g., hydrophilic or hydrophobic coating) to at least a portion of the rotating chamber, such as the flat 608 at the end of the wedge 609 to prevent some of the captured BC from remaining on the flat due to surface tension. Furthermore, there may be a benefit in providing an angle (e.g. 1 to 45 degrees) to the flat of the wedge, in order to direct the flow of fluid towards the central collection area, if in a generally vertical orientation.

It has been observed that causing the rotation chamber to decelerate rapidly lead to an increase in the amount of platelets in the collection area, relative to a more gradual deceleration of the rotation chamber. It is believed the rapid deceleration will create mixing of the components above the flat of the wedge, and avoids the occurrence of residual concentrated buffy coat components remaining on the surface of the flat of the wedge. It is believed that the red blood cells remaining within the chamber and within the channel, will remain largely contained within the channel, and not mix with the buffy coat, even upon rapid deceleration.

The geometry of the embodiments of the device incorporating the wedge 609 provides at least 3 benefits aiding in the efficiency, and operation of the device, as the wedge 609 serves to: 1) create spatial separation; 2) form the channel; and 3) increase the apparent depth of liquids. First, the wedge creates spatial separation between the outlets for the plasma and the RBC, and therefore can minimize the effects of shear forces at the outlet from affecting the buffy coat components which remain distant alongside the flat of the wedge. Second, the wedge partially forms the channel, as the outermost surface of the wedge, at angle b, provides part of the inner boundary of the channel 640. Third, the wedge enhances the ease of operating the device, as it enhances the apparent depth of the liquids displaced by the existence of the wedge. That is, the wedge serves to displace the volume of the fluids that are in the wedge region (between D2 and D8), and has the effect of increasing the apparent depth of these liquids, as dimensions between D4 and D5 are increased due to the displacement, and necessarily the spacing between markers 644, at L4 and L5, can accordingly be made larger and provide greater resolution for the operator. With the effect that the operator can now more accurately determine when to halt the discharge of the RBC through the RBC passage 639.

FIG. 21 shows the device of FIG. 19 assembled and in the running state with the RBC port 638 open, the plasma port 612 closed, and the RBC discharged to the RBC-Plasma receiver 647. No plasma 643 has yet been discharged to the receiving chamber. The air core 646 is fully established and the separated fluid components are established with clear boundaries. The spinning centrifuge blood-containing chamber is made up from two elements, the tapered barrel 606 and the end cap 614. This chamber spins in two bearings 619 and 604, the smaller bearing 604 locating the narrow end of the chamber, and the larger bearing 619 locating the larger end of the chamber indirectly via the drive shaft 617 and the valve cap 616. The smaller bearing 604 is mounted in the transparent mid cover 607 and the larger bearing in follower 618. Valve cap 616 rotates with the chamber components driven by a key or pin (not shown) from the end cap 614, and can translate axially along the rotation axis propelled axially by the follower 618, which in turn is moved axially by cam followers 620 and cams 621. Axial movement of valve cap 616 controls the position of RBC port 638 and plasma port 612, and thus controls the discharge of RBCs from RBC passage 639 or plasma from plasma passage 610. Cams 621 (typically 3 in number but may be more or less than 3) are integral with drum 613. Follower 618 can move axially within drum 613 but is prevented from rotation by male keys 631 on the follower and female keys on substructure 624. By rotating drum 613 the operator moves follower 620 axially and thus controls the position of the RBC and plasma ports 638 and 612. RBC-plasma receiver 647 surrounds the rotating elements to capture the discharged RBCs and excess plasma and moves axially with the valve cap 616.

Clearance between shaft 617 and valve cap 616, and the clearance between valve cap 616 and end cap 614 affects the fit and concentricity between end cap 614 and valve cap 616. ‘0’-rings 648 and 611 act as seals and/or act as suspensions between these two caps. If the clearances are held very small the ‘O’-rings act only as seals, but if the clearance is increased substantially the ‘0’-rings do double duty as seals and as suspensions. Such suspension characteristics can be selected so that the natural frequency of the valve cap 616 oscillating on the chamber assembly (shaft 617, end cap 614, and barrel 606) is substantially lower or substantially higher than the operating speed.

Centrifuge coupling 633 attached to drive shaft 617 accepts torsional drive from motor 626 via motor coupling 629. Motor 626 is mounted on substructure 624 that is fastened firmly to base enclosure 625. An operator activated latch 622 ensures that disposable portion 600 is firmly located relative to reusable portion 601 by engaging in an annulus integral with drum 613.

Disposable portion 600 arrives as a sterile unit and is used adjacent to a sterile field in an operatory environment. On completion of the procedure for preparing and applying PRP or PPP (which could involve running the device multiple times for multiple applications for a single patient) disposable portion 600 is discarded into the bio waste stream. However the reusable portion 601 remains in the operatory and may get moved elsewhere for storage. To ensure that no whole blood or blood components contaminate the reusable portion 601, a variety of elements may be employed to prevent the egress of these fluids. With reference to FIG. 26, absorbable washers 632 and 636 can capture any spillage from receiver 647, and gel accelerator 649 can cause the discharged fluids in receiver 647 to gel into a non-flowing gelatinous mass. Alternatively sealed bearings (not shown) at 619 and rolling diaphragms (not shown) between drum 613 and follower 618 can capture all liquids. Absorbable washers can be made from porous polyethylene (as sold under the tradename ‘Porex’), superabsorbent polymers, polyacrylates, polyelectrolytes, hydrogels, chalk, or woven textile, or other suitable materials known in the art. Gel accelerators can be made from materials as supplied by Multisorb Technologies, Inc. under the name Drimop®. Residuals of the PRP collected in the chamber are contained by port valve 602. Combinations of these solutions to leakage will also be clear to those skilled in the art.

Reusable portion 601 is powered by a cord mounted transformer (not shown) from an AC supply, or from a DC power pack such as those used for cordless drills and the like. Additional items not shown are (but not limited to) a simple display mounted on the base enclosure 625 that indicates power on-off to the centrifuge, elapsed time from power on, and may include items such an audible alarm for warning the operator when elapsed times reach certain levels. In addition hall-effect switches or reed switches (not shown) mounted in the base 625 which respond to magnets mounted in the disposable portion 600 can be used to indicate the rotation of drum 613 in base enclosure 625, and-or can be used to select varying motor speeds that might be necessary for optimum separation of fluid components.

Instead of an operator revolving drum 613 manually, actuators (e.g. motor-gearbox combinations or screw jacks) in the base 625 can rotate the drum automatically in response to signals from the switches described above and-or from a small solid state computer employed to optimize operation.

FIG. 22 is a simplified transverse section of FIG. 21 at AA. The blood has separated into its major components plasma 643, RBCs 641, and Buffy-coat (BC) at 642.

FIG. 23 is a simplified transverse section through BB of FIG. 21. This section shows the construction of the plasma valve consisting of passage 610, and ‘O’ ring 611. The construction of these outlet ports is similar to that shown in FIG. 3 b. When this valve is opened, port 612 will be moved to a position in alignment with passage 610, to allow for the flow of fluid therethrough.

FIG. 24 shows the device of FIG. 21 running in the situation where the RBC valve port 638 is closed, the plasma port 612 is open, and the plasma discharge has been completed. The volume of plasma 643 is the final volume.

When platelet poor plasma (PPP) is required for a procedure a slightly different configuration is required for the PPP receiver. FIG. 25 has most components similar to those shown in FIG. 21 but there are two receivers, one for RBCs 637 and one for PPP 635. Since two fluid components are captured by discharge from the spinning chamber the receivers both have to be fixed axially relative to drum 613 to accept the different axial locations of the plasma port 612 and RBC port 638 as they discharge appropriate fluid component. A plasma access port 645 spans the walls of the receiver 635 and extends through slot or opening (not shown) in drum 613. This port is of elastomeric material such as nitrile rubber that permits the passage of a hypodermic needle for the removal of the PPP.

In use the operator places a sterile disposable portion 600 into the reusable portion 601, the drum position being preset at the factory to the position where both plasma port 612 and RBC port 638 are closed. The operator then fills a syringe with whole blood from the patient and introduces the blood via the syringe through port valve 602 into the centrifuge chamber until the chamber is filled. The device is activated and the motor runs for about one minute by which time the blood has separated into the primary layers of RBC, buffy-coat, and plasma. At this time the drum is turned to position the RBC valve to the open position whereupon RBCs start to discharge into receiver 637. As the RBCs discharge the interface between RBCs and buffy coat (D5 in FIG. 20 a) approaches markings on the rotating barrel at 644 (L5 and L4 of FIG. 20 a). When the interface is between marks at 644 (about 30 seconds after the RBC port 638 is opened) the drum is turned to close the RBC port and open the plasma port 612. Plasma then discharges into the receiver and continues to do so until the air core limits further discharge. At this point (about 30 seconds after the plasma port was opened) the motor is stopped and the enriched residual sample in the chamber is removed via port 602 with a syringe and cannula for injection into the patient (or onto material about to be used as an implant). In the case of a PPP preparation the process is the same as that described for PRP except that the device conforms to the device shown in FIG. 25 and the PPP is extracted from the side elastomeric port 645 of FIG. 25.

It is recognized that by employing varying speeds of centrifugation, and altering the diameters at which the outlets from the chamber are placed, it is possible to concentrate different components, or isolate different density fractions of the fluid material within the rotation chamber. For example, rotating at a slower speed, as known to those skilled in the art, and removing the bulk of the RBCs as described above, will provide a plasma material with the suspended platelets. When rotated at lower speeds, the platelets will not differentiate by density from the plasma. Upon increasing the speed of rotation, the platelets will then tend to differentiate by density from the plasma, allowing flexibility in achieving the desired combination of blood products sought by the operator.

While the various embodiments discussed previously have described the blood separation chamber having a circular cross section, it is recognized that any shape capable of high speed rotation can be utilized, so long as there is an angled or tapered inner diameter to facilitate the appropriate flow of the red blood cells towards the RBC passage. For example, a separation chamber that provides an ovalized cross section may be employed, as it will be properly balanced and suitable for the rotational speeds required. Similarly, other separation chambers having cross-sectional profiles in varying shapes (e.g., octagonal, square, triangular, etc.) can be employed, and if necessary, balanced with weights to ensure proper balance when rotating. Furthermore, it is also recognized that multiple chambers may be utilized in the device, such as by providing 2 or more sections of a circle, or alternatively 2 or more vessels may be balanced to allow rotation of the multiple chambers, collectively forming a rotor, where each of the chambers would provide for discharge of particular blood components (e.g., RBC and Plasma), while allowing for the concentration and access to the desired blood component concentrated in each of the chambers.

The embodiments described herein are chiefly intended for use in separating components from whole blood, though they may be used with other liquids as well. In the case of blood product, once the device has been operated to stratify the blood into its constituent components, and the red blood cells and plasma removed from the blood separation chamber via the previously described RBC and plasma passages, the concentrated buffy coat containing platelets and white blood cells will remain within the chamber. In all the embodiments discussed, the operator of the device may further choose to clarify the resulting buffy coat by adding one or more additional biocompatible solutions, as a separation aid, into the device and optionally performing further centrifugation steps. These additional biocompatible solutions are sometimes referred to as focusing fluids. As previously described, the buffy coat consists of several constituents, including platelets and leukocytes (i.e. white cells), each having unique densities. The leukocytes contain granulocytes and lymphoid cells such as lymphocytes and monocytes, each of these having unique densities. For some applications, it may be important to isolate or remove one or several of these components from the buffy coat to provide a further purified therapeutic material. For instance, some researchers have found improved in vitro performance by removing leukocytes from the buffy coat (S. R. Mrowiec et al., A novel technique for preparing improved buffy coat platelet concentrates, Blood Cells, Molecules and Diseases (1995) 21 (3) Feb. 15: 25-23). By way of example, a fixed quantity of one or more liquids (e.g. focusing fluids) having specifically targeted densities could be delivered into the blood separation chamber to allow further separation of various components of the buffy coat (e.g. leukocytes) thereby focusing in upon a very specific sub-component of the blood. Alternatively, a focusing fluid may be used to enable the removal of all of the red blood cells or plasma, by being of a targeted density between the buffy coat and either the red blood cells or the plasma components, such that by repeating the concentration process described above, a blood component free from residual traces of either the plasma or red blood cells may be achieved. Such focusing fluids could include colorant, markers or other indicators to help distinguish the boundaries between the targeted and non-targeted biologic components. Fluids such as Ficoll-Paque sodium diatrizoate solution (density of 1.077 g/mL, distributed by GE Healthcare), Percoll (density of 1.088 g/mL, distributed by GE Healthcare), and Cellotion (distributed by Zenoaq) and other fluids known in the art could be used for purifying, separating and/or concentrating a wide variety of therapeutically beneficial cells and other biological constituents.

In another embodiment the biocompatible focusing fluid may selectively bind to a blood product and subsequently be isolated or separated by centrifugation, to result in a more concentrated desired blood component. Various techniques are known in the art for accomplishing the binding, for example, solid bead components of desired density may be coated with antibodies and employed to selectively bind the focusing fluid layer with the targeted blood component (or conversely, the blood component to be separated from the desired blood component). Alternatively, various techniques and reagents known to one skilled in the art, using techniques known, for example, from separation chemistry (e.g., chromatography or absorption) may be employed (such as ion exchange resins as used in HPL C and FPLC methodologies). In these embodiments, upon adding the focusing fluid to the blood separation chamber containing the previously concentrated blood product, and allowed an opportunity to bind, the desired blood product will be caused to separate from the unwanted blood product when the rotation is employed to stratify the materials within the blood separation chamber. Removal of separated products can proceed through one or both of the outlets as described previously. The binding of the focusing fluid in this embodiment may be reversible using techniques known in the art, such that upon being harvested, the blood component may be unbound from the focusing fluid, and optionally subjected to another purification procedure to provide harvested blood product free of any focusing fluid.

As before, with an operator or sensor causing the actuation of the valve mechanism controlling the discharge of fluids from the chamber, a detectable interface would be beneficial in determining when to close outlet valves. For this reason, the focusing fluid is preferably distinguishable in some manner at the interface with the other components within the chamber, for example, by being distinguishable by color. Alternatively, prior to the centrifugation with the focusing fluid, a biocompatible, selective dye or marker material may be added to distinguish the fluids withing the chamber, and create the interface that is detectable by the operator or sensor. Thus, the selective coloring would facilitate detection of an interface between the desired components, and those components sought to be removed from the blood separation chamber through one or both of the outlet ports.

The above described embodiments may be made available in kit form, including the device and accessories needed for operation of the device, including instructions for use and packaging suitable for storage and preserving sterility. In some instances, the kit may provide instructions along with the centrifuge device (either as a single unit, or separable components), and optionally including accessories such as separation aids, including focusing fluids. It is envisioned that the separation aids may be contained within a separate container within the packaging, or contained within the blood separation chamber during packaging, or made available apart from the centrifuge unit. For the embodiment providing a reusable drive component with a motor that is arranged to be coupled to a disposable centrifuge component, the kit may include multiple disposable centrifuge components each suitable for use with the reusable drive component.

Thus since the inventive process and inventions disclosed herein may be embodied by additional steps or other specific forms without departing from the spirit of general characteristics thereof, some of which steps and forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein. 

1. A medical device for the separation of the centrifuge-separable constituents of a liquid mixture said centrifuge comprising: a rigid chamber having a tapered circular section about a longitudinal axis and two closed ends, said chamber revolving about said axis and said chamber containing said liquid mixture as a discrete sample, prior to the initiation of rotation; means for rotating said chamber, whereby the mixture stratifies into its constituents by density as a function of radial distance from said axis; an orifice for the discharge of one or more of the denser constituents of said mixture, said orifice being located at or close to the maximum internal diameter of said chamber, said orifice revolving with said chamber and in fluid communication with the interior of said chamber; a valve means for opening and closing said orifice; means for monitoring said discharge when said orifice is open and said chamber is rotating, wherein said orifice is sized such that said discharge occurs over a time span such that a human operator can determine with precision when to actuate said valve means to close said orifice.
 2. The centrifuge of claim 1; wherein said stratification is detected by being visible to a human operator, and said valve means is operated manually.
 3. The centrifuge of claim 1, wherein said stratification is detected by an optical sensor, and said sensor automatically causes the actuation of said valve means.
 4. The centrifuge of claim 1, wherein said stratification is detectable as a differentiation of color or density at the outer surface of said tapered chamber.
 5. The centrifuge of claim 1, wherein said chamber is at least partially transparent.
 6. A centrifuge for selectively concentrating centrifuge-separable constituents of a liquid mixture, by withdrawing selected constituents from the centrifuge chamber upon separation, said centrifuge comprising: a) a chamber arranged to contain a liquid mixture, wherein said chamber comprises (i) a tapered tubular barrel comprising an interior with a larger interior diameter and a smaller interior diameter and a longitudinal axis, and further comprising a channel extending from the interior of the barrel to at least one orifice at the larger interior diameter of said tubular barrel, (ii) means for adding said liquid mixture to said chamber; (iii) means for discharging one or more constituents of said liquid mixture upon separation of said mixture, said discharging means comprising said at least one orifice, wherein said at least one orifice is positioned at a desired radius from said longitudinal axis and located in said channel, and further wherein said channel is arranged to reduce a velocity of the discharged constituents at the point of entry into the channel relative to the velocity of discharge through said orifice; b) a means to rotate the chamber about said longitudinal axis, whereupon said constituents of said liquid mixture separate as a function of radial distance from said longitudinal axis; and c) valve means for opening and closing said at least one orifice, where opening of said orifice during rotation of said barrel ejects at least a first constituent of the mixture that is present at said orifice, said ejection being through said opened orifice.
 7. The centrifuge of claim 6, wherein said channel further comprises a plenum adjacent said at least one orifice, said plenum combined with the channel are arranged to reduce the velocity of the discharged constituents at the point of entry into the channel relative to the velocity of discharge through said orifice.
 8. The centrifuge of claim 6, wherein the centrifuge further comprises: d) a vent to permit air to enter the center of the rotating chamber, to at least partially replace a volume of constituent removed.
 9. The centrifuge of claim 6, wherein at least a portion of the barrel comprises a transparent material.
 10. The centrifuge of claim 6, wherein the chamber further comprises a frusto-conical wedge extending inward from the larger side of the tapered chamber, and said chamber and frusto-conical wedge define the sides of the channel and plenum.
 11. The centrifuge of claim 6, further comprising a reusable component, and a disposable component capable of being operatively attached to the reusable component, and wherein the reusable component comprises a motor, and the disposable component comprises the chamber.
 12. The centrifuge of claim 11, wherein the disposable component further comprises at least one receiver arranged to capture blood product that is discharged from said rotating chamber.
 13. The centrifuge of claim 12, comprising a first receiver for red blood cells, and a second receiver for platelet poor plasma.
 14. The centrifuge of claim 12, wherein said at least one receiver further comprises a plasma access port.
 15. The centrifuge of claim 11, wherein said disposable component comprises absorbent blood product capturing materials.
 16. The centrifuge of claim 15, wherein the blood capturing materials comprise at least one of microporous polyethylene, superabsorbent polymers, polyacrylates, polyelectrolytes, hydrogels, chalk, and woven textile.
 17. The centrifuge of claim 13, wherein said receivers are arranged concentrically with the axis of rotation of the rotating chamber.
 18. A centrifuge for the separation of blood components, said centrifuge comprising a drive component and a blood separation chamber component, wherein said drive component and blood separation chamber component are releasably secured to each other, wherein said drive component, while in a secured position, drives the rotation of the blood separation chamber component to cause blood product to separate by density, and wherein said blood separation chamber component comprises a tapered barrel and a channel extending at an angle from the barrel, and having a plenum at the end of the channel with discharging means comprising at least one orifice positioned at a desired radius from said longitudinal axis and located in said plenum, and further wherein said channel and plenum are arranged to reduce a velocity of a first discharged constituent at the point of entry into the channel relative to the velocity of discharge through said orifice.
 19. The centrifuge of claim 18, wherein said drive component is reusable, and said blood separation chamber component is a single-use component.
 20. The centrifuge of claim 18, wherein said blood separation chamber component further comprises a wedge, said wedge extending into an interior of said tapered barrel, and, together with the tapered barrel, defining said channel.
 21. The centrifuge of claim 18, wherein said discharging means comprises a second orifice positioned at a second desired radius from said longitudinal axis and located at a base of said wedge.
 22. The centrifuge of claim 21, wherein said second orifice provides for the discharge of a second discharged constituent, wherein said second discharged constituent has a lower specific gravity than that of said first discharged constituent.
 23. A centrifuge for the separation of blood components, comprising a rotatable blood separation chamber comprising a tapered tubular barrel and an annular frusto-conical portion extending into the interior of the tapered tubular barrel, wherein said tubular barrel and annular frusto-conical portion are arranged to rotate about a axis, and wherein said tubular barrel and frusto-conical portion define a channel, wherein the blood separation chamber comprises means for adding blood to said blood separation chamber, means for rotating said blood separation chamber whereupon said blood separates into red blood cells, buffy-coat, and plasma, means for discharging a portion of said red blood cells, means for discharging a portion of said plasma, and means for collecting said buffy-coat.
 24. The centrifuge of claim 23, wherein said means for discharging a portion of said red blood cells comprises a valve means and a red blood cell opening located at a terminus of said channel furthest from said axis.
 25. The centrifuge of claim 23, wherein said means for discharging a portion of said plasma comprises a valve means and a plasma opening located at a larger end of said frusto-conical portion.
 26. The centrifuge of claim 23, wherein said means for discharging a portion of said plasma comprises a valve means and a plasma opening located at a radius smaller than the inner radius of the buffy coat.
 27. The centrifuge of claim 24, wherein said means for collecting said buffy-coat comprises a collection area located centrally to said tubular barrel, such that subsequent to discharging said portion of said red blood cells, and upon cessation of said rotation of said blood separation chamber, at least a second portion of said blood cells remain within said channel, and said buffy coat accumulates in said collection area.
 28. A centrifuge for the separation of buffy coat from whole blood, said centrifuge comprising a rotating chamber providing for separation of whole blood into distinct layers of red blood cells, buffy-coat, and plasma, the rotating chamber comprising a tubular cylinder having one end larger than an opposite end, and further having geometry at the larger end that provides for passage of red blood cells along a radially shallow channel from which at least one orifice provides for the discharge of red blood cells from the rotating chamber, and where said channel is arranged to reduce a velocity of the exiting red blood cells at the point of entry into the channel relative to the velocity of discharge through said at least one orifice.
 29. The centrifuge of claim 28, wherein said channel further comprises a plenum adjacent the at least one orifice.
 30. The centrifuge of claim 28, wherein said reduction of velocity is by a factor of at least 100:1.
 31. The centrifuge of claim 6, wherein said valve means comprises a valve cap comprising at least one port for said at least one orifice, and further wherein said discharging occurs when said at least one port is in axial alignment with said at least one orifice.
 32. The centrifuge of claim 31, wherein said valve cap rotates with said chamber.
 33. The centrifuge of claim 31, wherein said valve cap is translated axially along the rotational axis by at least one follower.
 34. The centrifuge of claim 33, wherein said at least one follower is translated axially by rotating a drum that is coaxial with respect to said chamber.
 35. The centrifuge of claim 23, wherein said means for adding blood comprises a port.
 36. A centrifuge for concentrating selected constituents of a liquid mixture by withdrawing undesirable constituents from the centrifuge chamber as the machine is running, said centrifuge comprising: a rotatable chamber having a longitudinal axis of rotation into which the sample of liquid is placed prior to rotation, and having an outer wall which is at an angle to the axis of rotation; one or more channels connecting the interior of said chamber, at least one orifice, and at least one valve, to a non-rotating area adjacent said chamber, through which said undesirable constituents are discharged, said channels providing for low entry velocity for said undesirable constituents at an interface with said selected constituent relative to the velocity of said undesirable constituents as they approach said orifices; valve operating means for opening and closing said at least one valve during rotation of said chamber; and means to rotate said chamber.
 37. The centrifuge of claim 36, wherein said means to rotate said chamber comprises a drive unit that is releasable secured to said centrifuge chamber.
 38. The centrifuge of claim 36, wherein said one or more channels further comprise one or more plena at an end of the channel adjacent said at least one orifice.
 39. A centrifuge for the separation of buffy coat from whole blood, said centrifuge comprising a rotating chamber providing for separation of whole blood into distinct layers of red blood cells, buffy-coat, and plasma, the rotating chamber comprising a tubular cylinder having one end larger than an opposite end, and further wherein the chamber further comprises a frusto-conical wedge extending inward from the larger end, and said chamber and frusto-conical wedge define the sides of a radially shallow channel that provides for the passage of red blood cells, and from which at least one orifice provides for the discharge of red blood cells from the rotating chamber, and where said channel is arranged to reduce a velocity of the exiting red blood cells at the point of entry into the channel relative to the velocity of discharge through said at least one orifice.
 40. The centrifuge of claim 39, wherein said channel further comprises a plenum adjacent said at least one orifice.
 41. The centrifuge of claim 39, wherein said frusto-conical wedge further comprises a flat.
 42. The centrifuge of claim 41, wherein said flat is at an angle relative to an axis of rotation.
 43. A centrifuge for the separation of the constituents of a liquid mixture, said liquid mixture comprising at least a first constituent of high specific gravity, a second constituent of low specific gravity, and a third constituent of an intermediate specific gravity, said centrifuge comprising: a rigid chamber having a tapered circular section about a longitudinal axis and two closed ends, at least a portion of said chamber being transparent, said chamber revolving about said axis and said chamber containing said liquid mixture prior to the initiation of rotation, means for rotating said chamber at sufficient speed for a gaseous core to occur around the axis of rotation as constituents of said chamber are discharged, at least two orifices placed at different radii from the axis of rotation for the discharge of at least two of said constituents from said chamber, said orifices revolving with said chamber and in fluid communication with the interior of said chamber, a first valve means for opening the radially outermost orifice to the area surrounding said chamber as said chamber revolves after said liquid mixture has separated and stratified into its several constituents, said stratification between the highest density constituent and the intermediate density constituent being detectable to a human operator as a differentiation of color at the outer surface of said tapered chamber for the purposes of closing said first valve when said stratification line reaches a predefined location on said transparent portion of said chamber, thus retaining a predefined quantity of said first constituent in said chamber second valve means for opening the radially innermost orifice to the area surrounding said chamber as said chamber revolves for the discharge of said second constituent, said second constituent continuing to discharge until said gaseous core radius reaches said second orifice when said discharge of said second constituent is physically prevented by the presence of said gaseous core, the location of said first and second orifices and the geometry of said chamber defining a precise residual volume of said first constituent, a precise residual volume of said second constituent, and the capture of substantially all of the third constituent.
 44. A method of concentrating selected constituents of blood, comprising the steps of: a. providing a centrifuge device comprising a rotatable chamber comprising a tubular cylinder having one end larger than an opposite end, and further wherein the chamber further comprises a frusto-conical wedge extending inward from the larger end, and said chamber and frusto-conical wedge define the sides of a radially shallow channel that provides for the passage of red blood cells, and from which at least one orifice provides for the discharge of red blood cells from the rotating chamber, and where said channel is arranged to reduce a velocity of the exiting red blood cells at the point of entry into the channel relative to the velocity of discharge through said at least one orifice, at least one channel; b. adding blood into said rotatable chamber; c. rotating said rotatable chamber, whereupon said components separate by density into red blood cells, buffy-coat, and plasma; d. opening a valve to allow the discharge of red blood cells through said at least one orifice; and e. closing said valve when a desired portion of said red blood cells has been discharged.
 45. The method of claim 44, further comprising the steps of: e. opening a second valve wherein a second orifice provides for the discharge of plasma component; and f. closing said valve when a desired portion of said plasma has been discharged.
 46. The method of claim 44, wherein said blood also contains at least one focusing fluid.
 47. The method of claim 46, wherein said at least one focusing fluid has a density intermediate that of platelets and leukocytes.
 48. The method of claim 46, wherein said at least one focusing fluid has a density intermediate that of RBCs and buffy coat.
 49. The method of claim 46, wherein said at least one focusing fluid has a density intermediate that of buffy coat and platelets. 